Two-Temperature Transport Coefficients in Argon–Hydrogen Plasmas—I: Elastic Processes and Collision Integrals

The calculation of two-temperature transport coefficients in an argon–hydrogen plasma at atmospheric pressure is performed using a new theory of two-temperature transport properties recently presented. The latter takes into account the coupling between electrons and heavy species, coupling neglected in the already existing theories of Devoto and Bonnefoi. Transport coefficients are calculated at two-temperatures, the kinetic temperature of electrons T_e being different from that of heavy species T_h. This paper is divided into two parts. The first one is related to elastic processes and its aim is to compare the results obtained with this new theory for viscosity , translational thermal conductivities ^tr _e and ^tr _h and electrical conductivity with the previous results of Bonnefoi. The composition is calculated with the modified equilibrium constant of van de Sanden et al. and the most recent interaction potential are discussed. As it could be expected the electron translational thermal conductivity and the electrical conductivity calculated when taking into account or not the coupling between electrons and heavy species show non-negligible discrepancies. Besides this comparison, the results also show the drastic influence of the non-equilibrium parameter =T_e/T_h on the values of , , ^tr _e, and ^tr _h.     

Two-Temperature Transport Coefficients in Argon–Hydrogen Plasmas—II: Inelastic Processes and Influence of Composition

Recently, a two-temperature transport properties theory has been proposed that retains the coupling between electrons and heavy species in thermal plasmas where the kinetic temperature of electrons Te can be different from that of heavy species Th. This paper is devoted to the application of this approach to an argon–hydrogen mixture at atmospheric pressure, taking into account inelastic processes and considering chemical equilibrium. In this second part are studied: the development of a new method to calculate the reaction thermal conductivity (inelastic collisions) in a non-equilibrium (two-temperature) plasma taking into account the coupling between electrons and heavy species; the influence of the composition calculation methods comparing the modified equilibrium constant method used in part 1 to the stationary kinetic calculation one; the influence on the transport properties (, , ) of the composition calculation method and non-equilibrium parameter =T_e/T_h.The different plasma compositions obtained either through an equilibrium constant or a stationary kinetic method are first compared and, for example, for =1.6, a discontinuity at T_e=11,000 K and an ionization delay are observed in stationary kinetic calculation, relative to the equilibrium constant method. Electrical conductivity, viscosity as well as thermal conductivity, including the translational, internal and reactional contributions, are calculated up to 25,000 K. It is shown that the plasma composition has a strong influence on transport coefficients, inducing shifts or discontinuities in the curves of transport coefficients, depending on the chosen method of calculation.     

Deposition of Langmuir-Blodgett layers

The behavior of a liquid being pulled out along a vertical plate is discussed, assuming that, in equilibrium, the liquid has a finite contact angle _e . Using a simplified form of the Huh-Scriven analysis for viscous friction, we show that a steady state solution (with a dynamic contact angle< _e ) exists provided that the velocity of pull-outU is below a certain thresholdU _m(_e). These considerations can be transposed (with a modification in numerical coefficients) to the case where the liquid is covered with a surfactant monolayer, to be transferred towards the solid in theY mode. SinceU _m is predicted in terms of interfacial tensions, this may provide a general scheme of interpretation for reactive deposition.     

Evaluation of energy distribution on a heterogeneous surface from heat of adsorption and its application to the ammonia/Na-Y zeolite system

The— function (energy level function) which represents surface heterogeneity was derived from theq— function (experimental heat function) in the case of reversible adsorption. The Langmuir equation was extended and applied to the procedure of calculations. An iterative calculation led to the most probable— function by setting theq— function and adsorption temperature. As an example for actual cases, the— function of Na-Y zeolite was calculated from theq— function obtained by the measurement of heats of adsorption of ammonia at 373 K. The— function thus derived seemed to be consistent with the positional distribution of sodium ions.     

Studies of the wetting kinetics of liquid drops on solid surfaces

The viscosity _L and the surface tension _L of the liquid as well as the equilibrium contact angle _e are essential parameters governing the wetting kinetics of liquids on solids. By means of a contact angle apparatus with video image digitization, the dynamic contact angle and the radiusr of the contact area of sessile drops on solid surfaces have simultaneously been determined in dependence on time after drop application between about 3·10^–2 s and long times.The measurements were performed with series of liquids: polydimethylsiloxanes with different molecular masses and solutions of polyisobutylene in decalin and polyacrylic acid in water, covering a wide range of concentrations. The liquids in each series have a constant surface tension, but viscosities ranging over about four orders of magnitude, allowing the influence of _L and _L to be studied independently. Solids such as glass, polyethylene and polytetrafluoroethylene were chosen so that the cases of complete wetting (spreading) and partial wetting ( _e) could be studied.The curves of cos andr/R ₀ vs. time for the different liquids of a series can be superimposed to a master curve by plotting them against _L·t _L·R ₀, whereR ₀ is the radius of the original drop. All these master curves coincide at small wetting times, with exception of the data for the polysiloxanes. That means that the early stage of the wetting process is determined only by the properties of the wetting liquid. The influence of the solid surface, characterized by the equilibrium contact angle _e becomes significant only at the end of the wetting process.Dedicated to Professor Dr. H. Willersinn on the occasion of his 65^th birthday     

Some Anomalies in Coadsorption of Two Organic Substances Due to Differences in Molecular Interaction of Species Undergoing Coadsorption

Effect of molecular interaction between species undergoing coadsorption on the potential dependences of coverages ₁and ₂, surface tension, and equilibrium and nonequilibrium differential capacitances is analyzed on the basis of a set of isotherms for coadsorption of components 1 and 2 within a common monolayer when the EDL inner part obeys a model of three parallel capacitors. It is shown that, in a certain potential interval, at a certain ratio between adsorption parameters, the set of isotherms may have solutions that correspond to a minimum in a free energy surface, which is a function of ₁and ₂.     

Analytic matrix elements of the dipole moment and Herman-Wallis coefficients

Perturbation theory proves to be a powerful approach to obtain in analytic form both vibration-rotational energies and matrix elements of the dipole moment of diatomic molecules in terms of the expansion parameter = 2B _e/gw_e,B _e and _e being, respectively, the equilibrium rotational and harmonic vibrational spectral parameters. A systematic and efficient algorithm has been developed to execute such calculations with sufficient accuracy for most physical applications when the potential-energy function is accurately represented in the Dunham form. The method also provides analytic expressions of the Herman-Wallis coefficientsC _v ^v andD _v ^v for the vibration-rotational overtone bandsv ¹v for diatomic molecules in¹ electronic states.     

Interelectronic angle densities of atoms in momentum space

For the 102 atoms from He to Lr in their ground states, the Hartree–Fock interelectronic angle densities,¯A(¯₁₂), in momentum space are reported, where ¯₁₂ is the angle between the momentum vectorsp₁ and p₂ of two electrons. In the first three atoms, He–Be, ¯A(¯₁₂) is found to be uniform independent of ¯₁₂, while in the remaining 99 atoms,¯A(¯₁₂) is larger for a large ¯₁₂ than for a small ¯₁₂. Accordingly, the average interelectronic angles in momentum space are 90° precisely for the three atoms and greater than 90° for the 99 atoms.     

Kinetics of Gold Electrodeposition from Cyanide Electrolytes at a Monitored Surface Coverage by Thallium Atoms

A procedure for measuring kinetic parameters of gold electrodeposition in the presence of catalytically active thallium(I) ions while monitoring the coverage of the gold surface by thallium adatoms, , is described. The procedure accounts for the duration of contact between a freshly renewed surface of gold and a thallium-containing solution and assumes that the incorporation rate of thallium adatoms is proportional to and the current density of gold electrodeposition. At = const, kinetic dependences correspond to the Tafel equation. Values of and i ₀ increase with . At = 0.3, 0.6 and i ₀ 3 × 10^–4 A cm^–2, which conforms to values calculated from anodic curves obtained in similar conditions.     

Analysis of the Probability of the Mössbauer Effect in Iron(III) β-Diketonates

The probability of the Mössbauer effect f has been evaluated and the Debye temperatures of intermolecular vibrations _M at 295 and 78 K have been determined for ten Fe(III) -diketonates, which are complexes of molecular type. Variation of _M with temperature and molecular mass M has been found; in the latter case, _M decreases as M increases. As a result of this antibatic change in _M and M, the effect of a decreased energy of intermolecular interaction dominates the effect of increased molecular mass, and f decreases in conformity with the prediction provided by the molecular crystal model.     

Drag on a metallic or nonmetallic particle exposed to a rarefied plasma flow

Drag force on a metallic or nonmetallic spherical particle exposed to a plasma flow is studied for the extreme case of a free-molecule regime. Analytical expressions are derived for the drag components due to, respectively, atoms, ions, and electrons and for the total drag on the whole sphere due to all the gas species. It has been shown that the drag is proportional to the square of the particle radius or the drag coefficient is independent of the particle radius. At low gas temperatures with a negligible degree of ionization, the drag is caused mainly by atoms and could be predicted by using the well-known drag expression given in ordinary-temperature rarefied gas dynamics. On the other hand, the drag is caused mainly by ions at high plasma temperatures with a great degree of ionization. The contribution of electrons to the total drag is always negligible. Ignoring gas ionization at high plasma temperatures would overestimate the particle drag. There is a little difference between metallic and nonmetallic spheres in their total drag forces, with a slightly higher value for a metallic sphere at high plasma temperatures, but usually such a small difference could be neglected in engineering calculations. The drag increases rapidly with increasing gas pressure or oncoming speed ratio. For a two-temperature plasma, the drag increases at low electron temperatures but decreases at high electron temperatures with the increase in the electron/heavy-particle temperature ratio.Nomenclature C _d Drag coefficient - e Elementary charge - f _D,F _D Local and total drag (N/m ² andN) - f ^– Velocity distribution function for incident gas particles - f ⁺ Velocity distribution function for reflected gas particles - k Boltzmann's constant - m Gas particle mass (kg) - n Number density of gas species (m ^–3) - P ^–,P ⁺ Surface pressure due to incident and reflected gas particles - R ₀ Sphere radius (m) - S Speed ratio,S _j=U/(2kT _j/m_j)^1/2 - T _e,T _h Electron and heavy-particle (atom, ion) temperature - T _w Wall temperature - U Oncoming plasma flow velocity - v _x, v_y, v_z Velocity components of gas particles in thex, y, andz directions (m/sec) - v Thermal motion speed of gas particles,v _j =(8kT _j /m _j )^1/2 - v _ze Smallestv _z of electrons which could reach the sphere surface,v _ze=(2e/m _e)^1/2 (m/sec) - v _zw Value ofv _z of ions or electrons as arriving at the sphere surface (m/sec) - Center angle - Gas density (kg/m³) - Shear stress (N/m²) - Absolute value of the floating potential (V) - , Local and total particle fluxes incident to the surface - a Atoms - e Electrons - h Heavy particles - i Ions - j jth gas species - m Metallic sphere - mn Nonmetallic sphere A preliminary version of this paper was presented at the Eighth International Symposium on Plasma Chemistry held in Tokyo, September 1987.     

Activity coefficients for ternary systems: VI. The system HCl + MgCl2 + H2O at different temperatures; application of Pitzer's equations

Electromotive-force measurements have been made on HCl–MgCl₂–H₂O mixtures at 5, 15, 25, 35 and 45°C at eleven different ionic strengths from 0.1–5.0 mol-kg ^–1 . The results are interpreted in terms of the simple Harned's equations, as well as the more complicated Pitzer ion-component treatment of multicomponent electrolyte mixtures. Activity coefficients for HCl in the salt mixtures obey Harned's rule up to and including I=5.0. For the salt in the acid mixtures, Harned's rule holds true up to and including I=0.5. The contribution of higher-order electrostatic terms (E and E') in the Pitzer equations is important for accurate evaluations of unlike cation-cation interactions (_H,Mg), and cation-anion-cation interactions (_H,Mg,Cl). The values of^S_H,Mg and _H,Mg,Cl (determined with E and E'), _H,Mg and _H,Mg,Cl (determined without E and E'), as well as the trace activity coefficients of HCl, _tr ^A , in solutions of MgCl₂ (where ionic strength fraction of the salt,y _B = 1) at all the experimental temperatures and ionic strengths, are reported. Results of this study are compared with those for similar systems. At I=0.1 and 25°C, the results of the Brönsted-Guggenheim specific interaction theory are discussed briefly.     

Mechanical properties of oriented fibres of semicrystalline polymers based upon orientation function from optical properties

The computation of the orientational averages is a great problem in the case of semicrystalline polymers. In a previous communication [1] it has been shown that sin=f() sin describes the orientational changes satisfactorily for a certain class of polymers. In this paper some alternative deformation schemes are also discussed. It has been concluded that birefringence provides a useful guideline in the choice of a deformation scheme.     

Lattice modes of polyethylene

Summary The lattice modes of polyethylene with the phase differences ( and along the-axis and theb-axis were calculated at intervals of 30 for the phase differences. They wereT _x, T_y, T_x, T_y, R_z andR _z, and some special conditions of the phase differences separated the six modes. To know the reliability of the intermolecular force constants used in this calculation, the elastic moduli of polyethylene crystal along thea-axis and theb-axis were calculated with the modified potential functions and compared with the observed values.

---

Zusammenfassung Die Gitterschwingungen in PolyÄthylen mit den Phasendifferenzen und lÄngs dera- undb-Achsen wurden in Intervallen von 30 der Phasendifferenzen berechnet. Das gibt 6 Hauptschwingungen,T _x, T_y, T_x,T _y, R_z und R_z. Um die ZuverlÄssigkeit der intermolekularen Kraftkonstanten, die bei diesen Berechnungen verwendet wurden, zu prüfen, wurden die elastischen Moduln von PolyÄthylen-Kristallen in Richtung dera- undb-Achse unter bestimmten modifizierten PotentialverlÄufen berechnet und mit den beobachteten Werten verglichen.

     

Accurate electrical and spectroscopic properties ofX 1Σ+ BeO from coupled-cluster methods

Summary This paper reports a series of coupled-cluster (CC) calculations through CCSDT on the theoretically challenging ground state of the BeO molecule. Along with CC methods, quadratic configuration interaction (QCI) approximations to CC theory have been used (QCISD and QCISD(T)), which show several dramatic failings. Equilibrium electrical properties (, _xx , and _zz ) and basic spectroscopic properties (r _e, _e,D _e, and infrared intensity (I)) have been computed. Basis set and electron correlation effects are analyzed in order to arrive at accurate values of the dipole moment and polarizability, which are not known experimentally. For the dipole moment, we obtain a value of 6.25 D, with an uncertainty of about 0.1 D. For _xx and _zz , we suggest respective values of 32 and 36 atomic units (a.u.) and error bars of about 1 and 2 a.u. With extended basis sets, the spectroscopic propertiesr _e, _e, andD _e are reproduced to high accuracy, which is the first time this has been achieved for this species byab initio methods. At the highest calculation levels,I is predicted to be very small. AlthoughI has not been measured, some support for this prediction comes from a recent infrared study of BeO-rare gas complexes. The QCI methods are shown to be much more sensitive to basis set, and even with large basis sets yield values of _zz andI which differ from CC results by an order of magnitude and three orders of magnitude, respectively. These differences doubtless arise from the importance of single excitations (T ₁) for this molecule, as several terms involvingT ₁ are neglected in the QCISD approximation compared with CCSD. We also report CC calculations with Brueckner orbitals, which yield results similar to those obtained with restricted Hartree-Fock orbitals.     

Epitaxially Grown LaSrCoO3 Thin Films on Various Substrates by the Sol-Gel Method

LaSrCoO₃ thin films have been prepared on various substrates by the sol-gel method using inorganic salts as starting materials. The crystallinity and in-plane alignment of the films were analyzed by X-ray diffraction -2 scans and scans (pole-figure analysis), respectively. Highly (h00)/(00l)-oriented LaSrCoO₃ films with crack-free surfaces were obtained by annealing at 800°C on SrTiO₃(100), while films grown on MgO(100) and Si(100) exhibited poor crystallinity. According to the X-ray diffraction -2 scan, crystallinity of the product films was found to depend on lattice-misfit values between the films and the substrates used. On the contrary, the lattice-misfit values were less effective to the epitaxy of the LSCO film. Epitaxial film grown on SrTiO₃ annealed at 800°C was found by reciprocal-space mapping (-2 scan) analysis to consist of the pseudocubic phase.     

The Hydrophobicity Study of Silica and Glass Surfaces Modified with Polyalkylhydrosiloxanes

A procedure based on the analysis of the shape of a sessile drop was used to measure the contact angles of water in air, _a = 93°–97°, for quartz and glass plates modified with polyalkylhydrosiloxanes. The specific heat of wetting, q = 36 mJ/m², and the surface pressure of adsorbed water film, = 48 mJ/m², were determined from adsorption-calorimetric experiment on macroporous disperse silica modified with polymethylhydrosiloxane GKZh-94M. The contact angle in saturated water vapors, _v = 84°, was calculated from these values. It was shown that the liquid-phase modification of silica and glass with polyalkylhydrosiloxanes leads to distinct hydrophobization of the studied surfaces.     

A calorimetric investigation into copper–arginine and copper–alanine solid state interactions

Complexes of formula CuCl₂ · 2arg and CuCl₂ · 4ala (arg = arginine; ala = alanine) were prepared at room temperature by a solid state route. The metal–amino acid solid state interactions were studied by i.r. spectroscopy and solution calorimetry. For both complexes, participation of the carboxylate group as well as nitrogen in coordination are inferred, based on the i.r. data. For the copper–arginine compound, the calculated thermochemical parameters are: _rH_m = –114.9 ± 1.42 and _fH_m = –1608.3 ± 11.6 kJ mol^–1. For copper–alanine compound, a complete set of thermochemical parameters were calculated: _rH_m = –18.0 ± 0.9; _fH_m = –2490.4 ± 4.3; _DH_m = 597.2 ± 17.7; _MH_m = 771.9 ± 18.7; _gH_m = 627.1 ± 22.3 and D (Cu–L) = 156.8 ± 5.7 kJ mol^–1. Based on _rH_m and dissolution enthalpy values, a stronger intermolecular solid state interaction can be inferred for the arginine complex, than for the alanine one complex, probably due to the formation of intermolecular hydrogen bonds in the former.     

Effects of adsorbed bismuth on Si(001) surface electronic states

It is shown that depositing Bi on an Si(001) surface fills the free broken-bond surface states, whose concentration decreases linearly as the bismuth coating 8 increases up to _st, = 0.6 monolayer. The bismuth desorption activation energy is constant < _st, (E_d = 2.77 ± 0.1 eV) and decreases for > _st.Taras Shevachenko Kiev National University, ul. Vladimirskaya 64, 252601 Kiev-17, Ukraine. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 32, No. 3, pp. 168–171, May–June, 1996. Original article submitted September 19, 1995.     

Estimation of heat of adsorption from energy distribution on heterogeneous surfaces by a theoretical analysis of adsorption process

An attempt was made to calculate theq— function (experimental heat function) from the— function (energy level function) of a heterogeneous surface. In order to obtain the heat of adsorption, adsorption was assumed to take place on each energy level of the— function. In reversible adsorption, Langmuir's monolayer model was extended to determine the occupation of energy levels by molecules. On this basis, the heat of adsorption could be calculated. Irreversible adsorption was also examined on the basis of chemical kinetics. Molecules were supposed to be held on sites to which they first collided. These calculations were useful for estimating the extent of deviation of theq— function from the— function.